According to the "2010 Social Indicators in Korea" announced by the National Statistical Office, Korea was already an aging society in 2000 with the aged accounting for 7% of the general population. By 2018 the aged will make up 14.3% of the Korean population, and by 2026 Korea will be considered a super-aged society with the aged constituting over 20% of the population1. In addition, the incidences of chronic diseases have increased, as has interest in healthy lifestyles. Statistics on cancer, the number one cause of mortality, are considered especially important to compile2. The Korean government has been asked to devise and enforce comprehensive policies for cancer. Accurate statistics are necessary to establish optimal cancer management policies.

The Central Cancer Registry Project was started in 1980 in various hospitals based on the National Medical Center. In 2000, the Central Cancer Registry Project headquarters were transferred to the newly founded National Cancer Center. The Korean government enacted a cancer management law in 2003, and established the National Cancer Center along with local units in 2004 to implement a nationwide population-based cancer registry project3.

To improve the overall reliability of cancer incidence data, the National Cancer Center conducts statistical surveys on cancer incidence among unregistered individuals who are suspected of having cancer based on National Health Insurance data and has established a national cancer incidence database by incorporating data from all of the cancer registry projects conducted in Korea. The National Cancer Center also supports the cancer registry projects of clinical academies and research councils to calculate accurate survival rates for each stage of each cancer type. As a result, the national cancer registry project has published an annual report since 2005 based on national cancer incidence statistics, and the scope of the announcements has been expanded to include statistics for cancer survival in 2008 and statistics for cancer prevalence in 20093.

However, the data for cancer incidence as presented by annual reports of the national cancer registry project were based on patients who were diagnosed with cancer between January 1 and December 31 2008, but also included cancer patients registered until November 2009. Therefore, statistics for cancer incidence may differ based on the time of announcement, and there is overlap among patients with multiple cancers in the calculations. Despite these shortcomings, the collection, management, analysis, and accurate presentation of statistics is important for national cancer management and research3. Nonetheless, oral and maxillofacial cancers (OMFCs) have attracted less attention from the Korean government than other cancers because they have high incidence rates in developing countries, but low incidence rates relative to the overall cancer incidence rate in most advanced countries4. In 2009, however, 3.1 males and 0.9 females per 100,000 people died of oral cancer, and the number of oral cancer patients is increasing2. In America, 30,000 cases of oral cancers develop and 7,000 people die of oral cancer annually5. Therefore, in the present clinical statistical analysis, we divided and sorted OMFCs based on the national cancer registry statistics from 20083.

OMFCs were divided into 10 areas: lip, tongue, mouth, salivary glands, tonsil, oropharynx, nasopharynx, hypopharynx, pharynx unspecified, nose and sinuses. These are areas treated by head and neck surgery. Melanoma around the mouth was not included in this classification. We conducted this research to obtain necessary data to establish cancer management policies for OMFCs, to develop early diagnosis and treatment plans for oral cancers, to improve survival rates, and to help define the direction and scope of diagnosis by oral and maxillofacial surgeons.

We divided and sorted cancers in the oral and maxillofacial area based on data from the annual national cancer registry report for 2008. The incidence rates for each OMFC were divided into 10 OMFC types among a total of 61 cancers based on the C15 standard of the 9th edition of Cancer Incidence in Five Continents published in 2007 by the International Agency for Research on Cancer3. When divided into 24 categories based on major cancers, malignant neoplasms in the lip, mouth, and pharynx were classified as C00-C14. In the 24-cancer classification, C30-C31 cancers (nasal cavity and paranasal sinuses in the oral and maxillofacial area) were excluded.

Cancers in the oral and maxillofacial area were divided into 15 areas and subsequently incorporated into 10 areas. Malignant neoplasms of the base of the tongue (C1) and other and unspecified parts of the tongue (C2) were categorized as tongue cancer; malignant neoplasms of the gums (C3), floor of the mouth (C4), palate (C5), and other and unspecified parts of the mouth (C6) were categorized as mouth cancer. Malignant neoplasms of the parotid gland (C7) and other and unspecified parts of the salivary glands (C8) were categorized as salivary gland cancer; malignant neoplasms of the pyriform sinus (C12) and hypopharynx (C13) were categorized as hypopharyngeal cancer, and malignant neoplasms of the nasal cavity and middle ear (C30) and accessory sinuses (C31) were categorized as cancers of the nose, and sinuses.(Table 1)

In this study, the estimated crude rate (CR) of each cancer was calculated by dividing the total population by the number of cancer patients occurring in a specific group during the research period. The estimated CRs are expressed per 100,000 people. The age-standardized incidence rate (ASR) is a weighted average rate calculated by applying the rate of the standard population to each age group as a weighted value. The ASR is used to compare cancer incidence rates in locations or during periods with different age compositions and is expressed as the rate per 100,000 people after revision based on the mid-year registered population in 2000. Annual percent change (APC) is an index that summarizes the trend of cancer incidence and is calculated by applying the exponential function to the incline of the linear trend curve of the logapplied annual ASR. The APC is interpreted as the annual average percent change of cancer incidence rate. The 5-year prevalence indicates the number of cancer patients surviving for 5 years, starting on January 1 the year after the standard year.

Malignant melanoma around the mouth was excluded from the present analyses. Although it is assumed to be included in category C43 (malignant melanoma on skin), it is difficult to classify precisely because it is not explicitly included in the annual reports that we used for references. Moreover, the sums of CR and ASR were sorted into one category (C00-C014) in the annual reports, but we recorded it by adding figures in C30-C31 to the existing figures. In addition, cancer patients may have been assigned to regions different from those where they actually lived the longest because they were categorized based on current addresses. Therefore, the interpretations of incidence rates per region may be inaccurate.

The incidence rates of oral cancer differ by race, region, and other conditions6,7. In this analysis, the incidence of OMFC in Korea was 1.6%. As a comparison, nearly 50,000 people in Europe developed oral cancer in 1995 to account for 2% of the total cancer incidence rate8, which is similar to the result obtained in this study. With respect to the incidence rate by sex, Funk et al.9 found that for oral cancer patients in America, male patients outnumbered female patients at a ratio of 60 : 40. Moreover, Abreu et al.10 found that male patients outnumbered female patients at a ratio of 2.4 : 1 in Australia. In Korea, Kim et al.11 reported that there were more male oral cancer patients than female patients. According to Cho et al.12, there were 2.7 times more male Korean oral cancer patients than female patients. In this analysis, the ratio between males and females was 2.72 : 1. With respect to age group, the 60-69 age group exhibited the highest incidence in both sexes. Chandu et al.13 reported the average age to be 62.6, with 61.1 for males and 64.5 for females. According to Funk et al.9, the average age was 64. However, the incidence rate of cancer tended to decrease among people aged 80 and over. This may not indicate that the actual cancer incidence rate is low in older age patients; rather, the cancer incidence rate appears to be lower than the actual rate because medical institutions higher than the hospital level do not frequently diagnose people in that age group as cancer patients.

The most common OMFC was mouth cancer, followed by tongue cancer and nasopharyngeal cancer. With respect to 5-year prevalence, the most common cancer was tongue cancer followed by nasopharyngeal cancer and mouth cancer, with differences by region and population origin. Warnakulasuriya14 and Zini et al.15 reported that the most common cancer was lip cancer, which is very different from results from the domestic reports. In particular, the incidence rate of salivary gland cancer increased among females and younger people. Bjørndal et al.16, reported that the average age of patients was slightly different, but the ASR of salivary gland cancer was 0.8, which is similar to that reported in domestic research studies. In this analysis, the 5-year survival rate of cancer was 57.5%, while Cho et al.12 reported 57.63%, Layland et al.17 reported 44.6%, and Chandu et al.13 reported 83.3%. The continuous increase in cancer incidence is caused by increases in the number of elderly people, development of cancer diagnosis technology, popularization of early diagnosis, and westernization of eating habits. Drinking and smoking are the major causes of OMFC because, although rates of drinking and smoking have decreased worldwide since 2006, the incidence of drinking and smoking is highest among Organization for Economic Co-operation and Development member countries1. Many reports indicate that smoking combined with drinking significantly increases the possibility of oral cancer18,19. Further, oral status, chewing tobacco, working environment, viral infection, weakened immune system, and stress may also cause oral cancer20,21. Increases in cancer survival rates in both sexes may be due to improvements in cancer diagnosis and treatment technologies, and improvements at the level of the national cancer management project.

Social and personal efforts may be required to increase the survival rates of OMFC patients, including early detection and diagnosis of oral cancer, regular diagnosis, and education to improve patient lifestyles, specifically with respect to smoking and drinking. The increases in cancer incidence and survival rate lead to increases in the number of cancer patients. Therefore, Korean national cancer management policy should establish new measures for economic and social management and support for surviving cancer patients. Finally, oral and maxillofacial surgeons should continually work to develop anticancer treatments, radiotherapy, and oral cancer surgeries, while also participating in gene therapy22, radiation surgery such as cyber knife techniques23, and immunohistochemical research.